Secondary battery and assembly therefor

ABSTRACT

The present disclosure provides a secondary battery and an assembly therefor. The secondary battery comprises: a cap plate provided with a first electrode terminal and a second electrode terminal; an electrode assembly comprising a first electrode tab and a second electrode tab; a first connecting piece connected between the first electrode tab and the first electrode terminal. The first connecting piece includes a first electrode terminal connecting portion, a first electrode tab connecting portion and a first fusing portion. The secondary battery further comprises an insulating holding block, two ends of which are connected with the first electrode terminal connecting portion and the first electrode tab connecting portion respectively, and the insulating holding block is configured to maintain the first electrode terminal connecting portion and the first electrode tab connecting portion in position relative to each other when the first fusing portion is fused.

CROSS-REFERENCE To RELATED APPLICATIONS

The present application claims priority to Chinese patent applicationNo. 201621318454.4, filed on Dec. 2, 2016, which is incorporated hereinby reference in its entirety.

FIELD OF THE PRESENT DISCLOSURE

The present disclosure relates to the field of battery, and particularlyrelates to a secondary battery and an assembly therefor.

BACKGROUND OF THE PRESENT DISCLOSURE

Referring to FIGS. 1-3, a first connecting piece 3 is generally used inthe prior art to fix a first electrode tab 21 of an electrode assembly 2to a first electrode terminal 11 of a cap plate 1, and the firstconnecting piece 3 is provided with a first fusing portion 33. When ahigh current flows through the first connecting piece 3, the firstfusing portion 33 can be fused in time so as to quickly cut off theelectrical connection between the first electrode tab 21 and the firstelectrode terminal 11, and prevent a thermal runaway of the secondarybattery. However, the first electrode terminal connecting portion 31 andthe first electrode tab connecting portion 32 of the first connectingpiece 3 will be separated from each other and become two independentparts after the first fusing portion 33 is fused, and when the electrodeassembly 2 is subjected to external impact and vibrates, the electrodeassembly 2 will bring the first electrode tab connecting portion 32 tomove up and down via the first electrode tab 21, the first electrode tabconnecting portion 32 will easily contact the first electrode terminalconnecting portion 31 to establish the electrical connection between thefirst electrode tab connecting portion 32 and the first electrodeterminal connecting portion 31 again, thereby resulting in thermalrunaway and causing explosion, so the first fusing portion 33 cannotfunction for safety protection.

SUMMARY OF THE PRESENT DISCLOSURE

In view of the problem existing in the background, an object of thepresent disclosure is to provide a secondary battery and an assemblytherefor, which can prevent thermal runaway of the secondary battery andimprove safety performance of the secondary battery.

In order to achieve the above object, in a first aspect, the presentdisclosure provides a secondary battery which comprises: a cap plateprovided with a first electrode terminal and a second electrodeterminal; an electrode assembly comprising a first electrode tab and asecond electrode tab; a first connecting piece connected between thefirst electrode tab and the first electrode terminal. The secondelectrode tab is electrically connected with the second electrodeterminal. The first connecting piece includes a first electrode terminalconnecting portion, a first electrode tab connecting portion and a firstfusing portion, the first electrode terminal connecting portion is fixedto the first electrode terminal, the first electrode tab connectingportion is fixed to the first electrode tab, and the first fusingportion is connected between the first electrode terminal connectingportion and the first electrode tab connecting portion. The secondarybattery further comprises an insulating holding block, two ends of theinsulating holding block are connected with the first electrode terminalconnecting portion and the first electrode tab connecting portionrespectively, and the insulating holding block is configured to maintainthe first electrode terminal connecting portion and the first electrodetab connecting portion in position relative to each other when the firstfusing portion is fused. In a second aspect, the present disclosureprovides an assembly for secondary battery which comprises a firstconnecting piece and an insulating holding block. The first connectingpiece includes a first electrode terminal connecting portion, a firstelectrode tab connecting portion and a first fusing portion, the firstfusing portion is connected between the first electrode terminalconnecting portion and the first electrode tab connecting portion. Twoends of the insulating holding block are connected with the firstelectrode terminal connecting portion and the first electrode tabconnecting portion respectively, and the insulating holding block isconfigured to maintain the first electrode terminal connecting portionand the first electrode tab connecting portion in position relative toeach other when the first fusing portion is fused.

The present disclosure has the following beneficial effects: in thesecondary battery and the assembly therefor according to the presentdisclosure, the first fusing portion is connected between the firstelectrode terminal connecting portion and the first electrode tabconnecting portion, therefore when a high current caused by overchargingor short circuit flows through the first connecting piece, the firstfusing portion will be fused in time so as to quickly cut off theelectrical connection between the first electrode tab and the firstelectrode terminal, and prevent thermal runaway of the secondarybattery; and when the first fusing portion is fused, the insulatingholding block maintains the first electrode terminal connecting portionand the first electrode tab connecting portion in position relative toeach other, and prevent the first connecting piece from becoming twoindependent parts at the fused position of the first fusing portion, andavoid contact between the first electrode tab connecting portion and thefirst electrode terminal connecting portion when the secondary batteryis subjected to external impact, and prevent the electrical connectionbetween the first electrode tab connecting portion and the firstelectrode terminal connecting portion from being established again,improve the safety performance of the secondary battery.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of a secondary battery in the prior art.

FIG. 2 is a cross sectional view of the secondary battery in the priorart.

FIG. 3 is an exploded view of the secondary battery in the prior art.

FIG. 4 is a schematic view of a secondary battery according to thepresent disclosure.

FIG. 5 is an exploded view of the secondary battery according to thepresent disclosure.

FIG. 6 is a cross sectional view of the secondary battery according tothe present disclosure.

FIG. 7 is a schematic view of a first electrode tab of the secondarybattery according to the present disclosure.

FIG. 8 is another schematic view of the first electrode tab of thesecondary battery according to the present disclosure.

FIG. 9 is a schematic view of a first connecting piece, an insulatingholding block and an insulating piece of the secondary battery accordingto the present disclosure.

FIG. 10 is an exploded view of FIG. 9.

FIG. 11 is a schematic view of the first connecting piece of thesecondary battery according to the present disclosure.

FIG. 12 is a perspective view of the insulating holding block of thesecondary battery according to the present disclosure.

FIG. 13 is a top view of FIG. 12.

FIG. 14 is a cross sectional view taken along a line A-A of FIG. 13.

Reference numerals in figures are represented as follows:

-   1 cap plate    -   -   11 first electrode terminal        -   12 second electrode terminal-   2 electrode assembly    -   21 first electrode tab        -   211 connecting section        -   212 bending section    -   22 second electrode tab    -   23 main body-   3 first connecting piece    -   31 first electrode terminal connecting portion    -   32 first electrode tab connecting portion        -   321 first electrode tab connecting sub-portion        -   322 first electrode tab jointing sub-portion    -   33 first fusing portion        -   331 opening        -   332 fusing sub-portion-   4 second connecting piece    -   41 second electrode terminal connecting portion    -   42 second electrode tab connecting portion        -   421 second electrode tab connecting sub-portion        -   422 second electrode tab jointing sub-portion-   5 insulating holding block    -   51 first holding portion        -   511 fixing post    -   52 second holding portion-   6 insulating bar-   7 insulating piece-   8 welding protecting piece-   H fixing hole-   G notch-   S insulating adhesive-   L length direction-   W width direction-   T thickness direction

DETAILED DESCRIPTION

Hereinafter a secondary battery according to the present disclosure willbe described in detail in combination with the figures.

Referring to FIGS. 4-14, a secondary battery according to the presentdisclosure comprises: a cap plate 1 provided with a first electrodeterminal 11 and a second electrode terminal 12 which are opposite inelectrical polarity; an electrode assembly 2 comprising a firstelectrode tab 21 and a second electrode tab 22 which are opposite inelectrical polarity; a first connecting piece 3 connected in seriesbetween the first electrode tab 21 and the first electrode terminal 11.The second electrode tab 22 is electrically connected with the secondelectrode terminal 12. The first connecting piece 3 includes a firstelectrode terminal connecting portion 31, a first electrode tabconnecting portion 32 and a first fusing portion 33, the first electrodeterminal connecting portion 31 is fixed to and electrically connectedwith the first electrode terminal 11, the first electrode tab connectingportion 32 is fixed to and electrically connected with the firstelectrode tab 21, and the first fusing portion 33 is connected in seriesbetween the first electrode terminal connecting portion 31 and the firstelectrode tab connecting portion 32. The secondary battery furthercomprises an insulating holding block 5, two ends of the insulatingholding block 5 are securely connected with the first electrode terminalconnecting portion 31 and the first electrode tab connecting portion 32respectively, and the insulating holding block 5 is configured tocapably maintain the first electrode terminal connecting portion 31 andthe first electrode tab connecting portion 32 in position relative toeach other when the first fusing portion 33 is fused.

In the secondary battery according to the present disclosure, the firstfusing portion 33 is connected in series between the first electrodeterminal connecting portion 31 and the first electrode tab connectingportion 32, therefore when a high current caused by overcharging orshort circuit flows through the first connecting piece 3, the firstfusing portion 33 will be fused in time so as to quickly cut off theelectrical connection between the first electrode tab 21 and the firstelectrode terminal 11, and prevent thermal runaway of the secondarybattery; and when the first fusing portion 33 is fused, the insulatingholding block 5 capably maintain the first electrode terminal connectingportion 31 and the first electrode tab connecting portion 32 in positionrelative to each other, and prevent the first connecting piece 3 frombecoming two independent parts (that is the first electrode terminalconnecting portion 31 and the first electrode tab connecting portion 32is separated from each other to become two independent parts) at thefused position of the first fusing portion 33, and avoid contact betweenthe first electrode tab connecting portion 32 and the first electrodeterminal connecting portion 31 when the secondary battery is subjectedto external impact (when the secondary battery is subjected to externalimpact, the electrode assembly 2 will vibrate, so the electrode assembly2 will bring the first electrode tab connecting portion 32 to move viathe first electrode tab 21, which may lead to the contact between thefirst electrode tab connecting portion 32 and the first electrodeterminal connecting portion 31), and prevent the electrical connectionbetween the first electrode tab connecting portion 32 and the firstelectrode terminal connecting portion 31 from being established again,improve the safety performance of the secondary battery.

In the secondary battery according to the present disclosure, referringto FIGS. 9-14, each of the first electrode terminal connecting portion31 and the first electrode tab connecting portion 32 is provided with athrough fixing hole H; correspondingly, the insulating holding block 5comprises a first holding portion 51 and a second holding portion 52.The first holding portion 51 is provided on one side of the firstconnecting piece 3 along a thickness direction T and includes fixingposts 511 which respectively correspond to the fixing hole H of thefirst electrode terminal connecting portion 31 and the fixing hole H ofthe first electrode tab connecting portion 32, and each fixing post 511passes through the fixing hole H and extends to the other side of thefirst connecting piece 3 along the thickness direction T. The secondholding portion 52 is provided on the other side of the first connectingpiece 3 along the thickness direction T and is securely connected withthe fixing posts 511 of the first holding portion 51 which respectivelypass through the fixing hole H of the first electrode terminalconnecting portion 31 and the fixing hole H of the first electrode tabconnecting portion 32. The first holding portion 51 and the secondholding portion 52 may be made of plastic.

In the secondary battery according to the present disclosure, theinsulating holding block 5 can be securely connected with the firstelectrode terminal connecting portion 31 and the first electrode tabconnecting portion 32 via cooperation between the first holding portion51 and the second holding portion 52. The second holding portion 52 maybe securely connected with the fixing posts 511 of the first holdingportion 51 by means of hot melting, interference fit, riveting,latching, adhering, inserting and the like, but it is not limited tothese above-mentioned connecting manners, and any other connectingmanners can be used as long as the fixing posts 511 of the first holdingportion 51 can be securely connected with the second holding portion 52.

In the secondary battery according to the present disclosure, each ofthe first electrode terminal connecting portion 31 and the firstelectrode tab connecting portion 32 is provided with a through fixinghole H; the insulating holding block 5 comprises a first holding portion51, the first holding portion 51 is provided on one side of the firstconnecting piece 3 along the thickness direction T and includes fixingposts 511 which respectively correspond to the fixing hole H of thefirst electrode terminal connecting portion 31 and the fixing hole H ofthe first electrode tab connecting portion 32, and each fixing post 511passes through the fixing hole H and is securely connected with thefirst connecting piece 3. The first holding portion 51 may be made ofplastic.

In the secondary battery according to the present disclosure, the fixingposts 511 may be securely connected with the first electrode terminalconnecting portion 31 and the first electrode tab connecting portion 32directly by means of hot melting, interference fit, riveting, adheringand the like, but it is not limited to these above-mentioned connectingmodes.

In the secondary battery according to the present disclosure, the fixinghole H is an oblong hole. A shape of the fixing post 511 corresponds tothe fixing hole H.

In the secondary battery according to the present disclosure, referringto FIGS. 9-11, the fixing hole H is a circular hole, and the fixing holeH of the first electrode terminal connecting portion 31 is provided asat least two in number, the fixing hole H of the first electrode tabconnecting portion 32 is provided as at least two in number. A shape ofthe fixing post 511 corresponds to the shape of the fixing hole H. In anembodiment that the first electrode terminal connecting portion 31 issecurely connected with the first electrode tab connecting portion 32via the cooperation between the first holding portion 51 and the secondholding portion 52, if the first electrode tab connecting portion 32only has one fixing hole H (in other words, only one fixing post 511passes through the first electrode tab connecting portion 32), when thefirst fusing portion 33 is fused and the secondary battery is subjectedto external impact, the first electrode tab connecting portion 32 willrotate around the fixing post 511, so as to cause the contact betweenthe first electrode tab connecting portion 32 and the first electrodeterminal connecting portion 31. Similarly, if the first electrodeterminal connecting portion 31 only has one fixing hole H, it will causethe above-mentioned problem too. But in another embodiment that thefixing posts 511 of the first holding portion 5 are securely connectedwith the first connecting piece 3 directly, the fixing hole H of each ofthe first electrode terminal connecting portion 31 and the firstelectrode tab connecting portion 32 may be provided as one in number.

In the secondary battery according to the present disclosure, referringto FIG. 10, the first fusing portion 33 is formed by providing anopening 331 in the first connecting piece 3, and the first fusingportion 33 includes fusing sub-portions 332 provided at two sides of theopening 331 respectively along a width direction W. The first holdingportion 51 further includes another fixing post 511 which passes throughthe opening 331.

In the secondary battery according to the present disclosure, referringto FIG. 11, the first fusing portion 33 is formed by providing notches Gin the first connecting piece 3, the notches G are provided at two sidesof the first fusing portion 33 respectively along the width direction W.

In the secondary battery according to the present disclosure, anovercurrent sectional area of the first fusing portion 33 is smallerthan an overcurrent sectional area of the first electrode terminalconnecting portion 31 and an overcurrent sectional area of the firstelectrode tab connecting portion 32 (due to provision of the opening 331or the notches G), therefore, when the high current flows through thefirst connecting piece 3, the first fusing portion 33 will be fused intime so as to quickly cut off the electrical connection between thefirst electrode tab 21 and the first electrode terminal 11, and preventthermal runaway of the secondary battery.

In the secondary battery according to the present disclosure, theelectrode assembly 2 is provided as multiple in number; correspondingly,referring to FIGS. 9-11, the first electrode tab connecting portion 32includes two first electrode tab connecting sub-portions 321 and a firstelectrode tab jointing sub-portion 322. The two first electrode tabconnecting sub-portions 321 extend along a length direction L, and eachfirst electrode tab connecting sub-portion 321 is fixed to andelectrically connected with the first electrode tab 21 of thecorresponding electrode assembly 2. The first electrode tab jointingsub-portion 322 extends along the width direction W, and two ends of thefirst electrode tab jointing sub-portion 322 are connected with the twofirst electrode tab connecting sub-portions 321 respectively. The firstelectrode terminal connecting portion 31 is positioned between the twofirst electrode tab connecting sub-portions 321 and extends along thelength direction L. The first fusing portion 33 extends along the lengthdirection L and is connected between the first electrode tab jointingsub-portion 322 and the first electrode terminal connecting portion 31.The first connecting piece 3 is planar in whole.

In the secondary battery according to the present disclosure, anextending direction and an arranging way of the two first electrode tabconnecting sub-portions 321 (the two first electrode tab connectingsub-portions 321 are the same as the first electrode terminal connectingportion 31 in the extending direction, and are positioned at two sidesof the first electrode terminal connecting portion 31 respectively alongthe width direction W) can increase a contact area between the firstelectrode tab 21 of the electrode assembly 2 and the corresponding firstelectrode tab connecting sub-portion 321, thereby increasing theovercurrent area.

In the secondary battery according to the present disclosure, referringto FIG. 4, the secondary battery further comprises two insulating bars6, each insulating bar 6 is provided in a gap between the firstelectrode terminal connecting portion 31 and the first electrode tabconnecting sub-portion 321, and each insulating bar 6 is not lower thana surface of the first connecting piece 3 which is connected with thefirst electrode tab 21 along the thickness direction T (in other words,each insulating bar 6 is not lower than a surface of the first electrodeterminal connecting portion 31 which faces a main body 23 of theelectrode assembly 2 along the thickness direction T). The firstelectrode tab 21 may extend beyond the gap and extend to the firstelectrode terminal connecting portion 31 if the first electrode tab 21is too long, thereby leading to a directly contact between the firstelectrode tab 21 and the first electrode terminal connecting portion 31,and resulting in a failure of the first fusing portion 33. Because thetwo insulating bars 6 are respectively provided in the two gaps and eachinsulating bar 6 is not lower than the surface of the first connectingpiece 3 which is connected with the first electrode tab 21 along thethickness direction T, the insulating bars 6 can function for isolationand prevent the first electrode tab 21 from electrically connecting withthe first electrode terminal connecting portion 31 (if each insulatingbar 6 is flush with the surface of the first connecting piece 3 which isconnected with the first electrode tab 21 along the thickness directionT, each insulating bar 6 can avoid the first electrode tab 21electrically connecting with a side wall of the first electrode terminalconnecting portion 31 which is used to form the corresponding gap, andif each insulating bar 6 is higher than the surface of the firstconnecting piece 3 which is connected with the first electrode tab 21along the thickness direction T, each insulating bar 6 can further avoidthe first electrode tab 21 contacting the surface of the first electrodeterminal connecting portion 31 which faces the main body 23 of theelectrode assembly 2). In addition, the “not lower than” and the “higherthan” are with respect to the thickness direction T as shown in FIG. 4,in other words, each insulating bar 6 is flush with the first connectingpiece 3 or is protruding from the first connecting piece 3 along adirection toward the electrode assembly 2 after the secondary battery isformed as a finished product as shown in FIG. 6.

In the secondary battery according to the present disclosure, referringto FIG. 4, FIG. 9 and FIG. 10, the secondary battery further comprisesan insulating piece 7 adhered on a surface of the first connecting piece3 which faces the electrode assembly 2 (specifically the main body 23 ofthe electrode assembly 2), and the insulating piece 7 at least coverstwo edges of the first electrode terminal connecting portion 31 whichare respectively positioned at two sides of the first electrode terminalconnecting portion 31 along the width direction W. The first electrodetab 21 may extend beyond the gap and extend to the corresponding edge ofthe first electrode terminal connecting portion 31 along the widthdirection W if the first electrode tab 21 is too long, thereby leadingto the direct contact between the first electrode tab 21 and the firstelectrode terminal connecting portion 31, and resulting in the failureof the first fusing portion 33; but the insulating piece 7 at leastcovers the two edges of the first electrode terminal connecting portion31 which are respectively positioned at the two sides of the firstelectrode terminal connecting portion 31 along the width direction W, sothe insulating piece 7 can isolate the first electrode tab 21 from thefirst electrode terminal connecting portion 31, and prevent the firstelectrode tab 21 from electrically connecting with the first electrodeterminal connecting portion 31.

In the secondary battery according to the present disclosure, referringto FIG. 7 and FIG. 8, the first electrode tab 21 includes a connectingsection 211 and a bending section 212. An outer side of the connectingsection 211 is securely connected with the first electrode tabconnecting portion 32; the bending section 212 bends and is connectedbetween the main body 23 of the electrode assembly 2 and the connectingsection 211, and an angle between the connecting section 211 and thebending section 212 is less than 120 degrees.

In the secondary battery according to the present disclosure, referringto FIG. 8, the angle between the connecting section 211 and the bendingsection 212 ranges from 85 degrees to 95 degrees. At this time, thebending section 212 extends nearly along the thickness direction T, soas to prevent short circuit caused by the bending section 212 when thebending section 212 is pressed down.

In the secondary battery according to the present disclosure, referringto FIG. 7, the angle between the connecting section 211 and the bendingsection 212 ranges from 0 degrees to 45 degrees. At this time, thebending section 212 nearly folds back onto the connecting section 211,thereby effectively reducing the space occupied by the first electrodetab 21, and promoting a utilization rate of the space inside thesecondary battery.

In the secondary battery according to the present disclosure, referringto FIG. 7 and FIG. 8, the secondary battery further comprises aninsulating adhesive S, the insulating adhesive S at least is adhered onan inside portion of the connecting section 211 which directly faces themain body 23 of the electrode assembly 2. When the cap plate 1 isassembled to a case (not shown)receiving the electrode assembly 2, thecap plate 1 will press down the first electrode tab 21 to easily resultin that the connecting section 211 (especially the portion of theconnecting section 211 which directly faces the main body 23 of theelectrode assembly 2) of the first electrode tab 21 will directlycontact the main body 23 (especially an electrode plate of the main body23 which is opposite to the first electrode tab 21 in electricalpolarity) of the electrode assembly 2, thereby resulting in shortcircuit; but it can avoid the short circuit of the electrode assembly 2and improve the safety performance of the secondary battery by provisionof the insulating adhesive S.

In the secondary battery according to the present disclosure, referringto FIG. 7 and FIG. 8, preferably, each of the inside portion of theconnecting section 211 and an inside portion of the bending section 212is covered by the insulating adhesive S.

In the secondary battery according to the present disclosure, referringto FIG. 7 and FIG. 8, the secondary battery further comprises aninsulating adhesive S adhered on an outside portion of the bendingsection 212. When the cap plate 1 is assembled to the case (not shown)receiving the electrode assembly 2, the first electrode tab 21 will bepressed down and bent, and the outside portion of the bending section212 will easily contact the case, thereby resulting in short circuit;but it can avoid the short circuit of the electrode assembly 2 andimprove the safety performance of the secondary battery by provision ofthe insulating adhesive S which covers the outside portion of thebending section 212.

In the secondary battery according to the present disclosure, referringto FIGS. 4-8, the secondary battery further comprises a weldingprotecting piece 8 provided on the first electrode tab 21; the weldingprotecting piece 8, the connecting section 211 of the first electrodetab 21 and the first electrode tab connecting portion 32 are securelyconnected together by ultrasonic welding. The welding protecting piece 8can improve connection strength between the connecting section 211 ofthe first electrode tab 21 and the first electrode tab connectingportion 32. An insulating adhesive tape is adhered on weld zones formedduring the ultrasonic welding. Metal chips generated during the weldingcan be fixed to the insulating adhesive tape, so the insulating adhesivetape can prevent the metal chips from entering into the inside of theelectrode assembly 2, also function for insulation and avoid theinternal short circuit of the electrode assembly 2.

In the secondary battery according to the present disclosure, referringto FIG. 4 and FIG. 5, the secondary battery further comprises: a secondconnecting piece 4 connected in series between the second electrode tab22 and the second electrode terminal 12.

In the secondary battery according to the present disclosure, referringto FIG. 4 and FIG. 5, the second connecting piece 4 includes: a secondelectrode terminal connecting portion 41 fixed to and electricallyconnected with the second electrode terminal 12; and a second electrodetab connecting portion 42 fixed to and electrically connected with thesecond electrode tab 22 of the electrode assembly 2.

In the secondary battery according to the present disclosure, referringto FIG. 4 and FIG. 5, the electrode assembly 2 is provided as multiplein number; correspondingly, the second electrode tab connecting portion42 includes two second electrode tab connecting sub-portions 421 and asecond electrode tab jointing sub-portion 422. The two second electrodetab connecting sub-portions 421 extend along the length direction L, andeach second electrode tab connecting sub-portion 421 is fixed to andelectrically connected with the second electrode tab 22 of thecorresponding electrode assembly 2. The second electrode tab jointingsub-portion 422 extends along the width direction W, and two ends of thesecond electrode tab jointing sub-portion 422 are connected with the twosecond electrode tab connecting sub-portions 421 respectively. Thesecond electrode terminal connecting portion 41 is positioned betweenthe two second electrode tab connecting sub-portions 421 and extends tothe second electrode tab jointing sub-portion 422 along the lengthdirection L.

In the secondary battery according to the present disclosure, anextending direction and an arranging way of the two second electrode tabconnecting sub-portions 421 (the two second electrode tab connectingsub-portions 421 are the same as the second electrode terminalconnecting portion 41 in the extending direction, and are positioned attwo sides of the second electrode terminal connecting portion 41respectively along the width direction W) can increase a contact areabetween the second electrode tab 22 of the electrode assembly 2 and thecorresponding second electrode tab connecting sub-portion 421, therebyincreasing the overcurrent area.

In the secondary battery according to the present disclosure, thesecondary battery further comprises: a welding protecting piece 8provided on the second electrode tab 22; the welding protecting piece 8,the second electrode tab 22 and second electrode tab connectingsub-portion 421 are securely connected together by ultrasonic welding.An insulating adhesive tape is adhered on weld zones formed by theultrasonic welding. Metal chips generated during the welding can befixed to the insulating adhesive tape, so the insulating adhesive tapecan prevent the metal chips from entering into the inside of theelectrode assembly 2, also function for insulation and avoid theinternal short circuit of the electrode assembly 2.

In the secondary battery according to the present disclosure, the firstelectrode terminal connecting portion 31 and the first electrodeterminal 11 are securely connected by laser welding, the secondelectrode terminal connecting portion 41 and the second electrodeterminal 12 are securely connected together by laser welding. Aninsulating adhesive tape is adhered on weld zones formed during thelaser welding. Metal chips generated during the welding can be fixed tothe insulating adhesive tape, so the insulating adhesive tapes canprevent the metal chips from entering into the inside of the electrodeassembly 2, also function for insulation and avoid the internal shortcircuit of the electrode assembly 2.

What is claimed is:
 1. A secondary battery, comprising: a cap plateprovided with a first electrode terminal and a second electrodeterminal; an electrode assembly comprising a first electrode tab and asecond electrode tab; a first connecting piece connected between thefirst electrode tab and the first electrode terminal; the secondelectrode tab being electrically connected with the second electrodeterminal; wherein the first connecting piece includes a first electrodeterminal connecting portion, a first electrode tab connecting portionand a first fusing portion, the first electrode terminal connectingportion is fixed to the first electrode terminal, the first electrodetab connecting portion is fixed to the first electrode tab, and thefirst fusing portion is connected between the first electrode terminalconnecting portion and the first electrode tab connecting portion; thesecondary battery further comprises an insulating holding block, twoends of the insulating holding block are connected with the firstelectrode terminal connecting portion and the first electrode tabconnecting portion respectively, and the insulating holding block isconfigured to maintain the first electrode terminal connecting portionand the first electrode tab connecting portion in position relative toeach other when the first fusing portion is fused.
 2. The secondarybattery according to claim 1, wherein each of the first electrodeterminal connecting portion and the first electrode tab connectingportion is provided with a through fixing hole; the insulating holdingblock comprises a first holding portion and a second holding portion;the first holding portion is provided on one side of the firstconnecting piece along a thickness direction and includes fixing postswhich respectively correspond to the fixing hole of the first electrodeterminal connecting portion and the fixing hole of the first electrodetab connecting portion, and each fixing post passes through the fixinghole and extends to the other side of the first connecting piece alongthe thickness direction; the second holding portion is provided on theother side of the first connecting piece along the thickness directionand is connected with the fixing posts of the first holding portionwhich respectively pass through the fixing hole of the first electrodeterminal connecting portion and the fixing hole of the first electrodetab connecting portion.
 3. The secondary battery according to claim 1,wherein each of the first electrode terminal connecting portion and thefirst electrode tab connecting portion is provided with a through fixinghole; the insulating holding block comprises a first holding portion,the first holding portion is provided on one side of the firstconnecting piece along a thickness direction and includes fixing postswhich respectively correspond to the fixing hole of the first electrodeterminal connecting portion and the fixing hole of the first electrodetab connecting portion, and each fixing post passes through the fixinghole and is connected with the first connecting piece.
 4. The secondarybattery according to claim 2, wherein the fixing hole is an oblong hole;or the fixing hole is a circular hole, and the fixing hole of the firstelectrode terminal connecting portion is provided as at least two innumber, the fixing hole of the first electrode tab connecting portion isprovided as at least two in number.
 5. The secondary battery accordingto claim 3, wherein the fixing hole is an oblong hole; or the fixinghole is a circular hole, and the fixing hole of the first electrodeterminal connecting portion is provided as at least two in number, thefixing hole of the first electrode tab connecting portion is provided asat least two in number.
 6. The secondary battery according to claim 1,wherein the first fusing portion is formed by providing an opening inthe first connecting piece, and the first fusing portion includes fusingsub-portions provided at two sides of the opening respectively along awidth direction; or the first fusing portion is formed by providingnotches in the first connecting piece, the notches are provided at twosides of the first fusing portion respectively along the widthdirection.
 7. The secondary battery according to claim 1, wherein theelectrode assembly is provided as multiple in number; the firstelectrode tab connecting portion includes two first electrode tabconnecting sub-portions and a first electrode tab jointing sub-portion;the two first electrode tab connecting sub-portions extend along alength direction, and each first electrode tab connecting sub-portion isfixed to the first electrode tab of the corresponding electrodeassembly; the first electrode tab jointing sub-portion extends along awidth direction, and two ends of the first electrode tab jointingsub-portion are connected with the two first electrode tab connectingsub-portions respectively; the first electrode terminal connectingportion is positioned between the two first electrode tab connectingsub-portions and extends along the length direction; the first fusingportion extends along the length direction and is connected between thefirst electrode tab jointing sub-portion and the first electrodeterminal connecting portion.
 8. The secondary battery according to claim7, wherein the secondary battery further comprises two insulating bars,each insulating bar is provided in a gap between the first electrodeterminal connecting portion and the first electrode tab connectingsub-portion, and each insulating bar is not lower than a surface of thefirst connecting piece which is connected with the first electrode tabalong a thickness direction.
 9. The secondary battery according to claim7, wherein the secondary battery further comprises an insulating pieceadhered on a surface of the first connecting piece which faces theelectrode assembly, and the insulating piece covers two edges of thefirst electrode terminal connecting portion along the width direction.10. The secondary battery according to claim 1, wherein the firstelectrode tab includes a connecting section and a bending section; anouter side of the connecting section is connected with the firstelectrode tab connecting portion; the bending section bends and isconnected between a main body of the electrode assembly and theconnecting section, and an angle between the connecting section and thebending section is less than 120 degrees.
 11. The secondary batteryaccording to claim 10, wherein the angle between the connecting sectionand the bending section ranges from 85 degrees to 95 degrees; or theangle between the connecting section and the bending section ranges from0 degrees to 45 degrees.
 12. The secondary battery according to claim10, wherein the secondary battery further comprises an insulatingadhesive adhered on an inside portion of the connecting section whichfaces the main body of the electrode assembly; and/or the secondarybattery further comprises an insulating adhesive adhered on an outsideportion of the bending section.
 13. The secondary battery according toclaim 10, wherein the secondary battery further comprises: a weldingprotecting piece provided on the first electrode tab; the weldingprotecting piece, the connecting section of the first electrode tab andthe first electrode tab connecting portion are connected together byultrasonic welding.
 14. An assembly for secondary battery, wherein theassembly for secondary battery comprises a first connecting piece and aninsulating holding block; the first connecting piece includes a firstelectrode terminal connecting portion, a first electrode tab connectingportion and a first fusing portion, the first fusing portion isconnected between the first electrode terminal connecting portion andthe first electrode tab connecting portion; two ends of the insulatingholding block are connected with the first electrode terminal connectingportion and the first electrode tab connecting portion respectively, andthe insulating holding block is configured to maintain the firstelectrode terminal connecting portion and the first electrode tabconnecting portion in position relative to each other when the firstfusing portion is fused.
 15. The assembly for secondary batteryaccording to claim 14, wherein each of the first electrode terminalconnecting portion and the first electrode tab connecting portion isprovided with a through fixing hole; the insulating holding blockcomprises a first holding portion and a second holding portion; thefirst holding portion is provided on one side of the first connectingpiece along a thickness direction and includes fixing posts whichrespectively correspond to the fixing hole of the first electrodeterminal connecting portion and the fixing hole of the first electrodetab connecting portion, and each fixing post passes through the fixinghole and extends to the other side of the first connecting piece alongthe thickness direction; the second holding portion is provided on theother side of the first connecting piece along the thickness directionand is connected with the fixing posts of the first holding portionwhich respectively pass through the fixing hole of the first electrodeterminal connecting portion and the fixing hole of the first electrodetab connecting portion.
 16. The assembly for secondary battery accordingto claim 14, wherein each of the first electrode terminal connectingportion and the first electrode tab connecting portion is provided witha through fixing hole; the insulating holding block comprises a firstholding portion, the first holding portion is provided on one side ofthe first connecting piece along a thickness direction and includesfixing posts which respectively correspond to the fixing hole of thefirst electrode terminal connecting portion and the fixing hole of thefirst electrode tab connecting portion, and each fixing post passesthrough the fixing hole and is connected with the first connectingpiece.
 17. The assembly for secondary battery according to claim 15,wherein the fixing hole is an oblong hole; or the fixing hole is acircular hole, and the fixing hole of the first electrode terminalconnecting portion is provided as at least two in number, the fixinghole of the first electrode tab connecting portion is provided as atleast two in number.
 18. The assembly for secondary battery according toclaim 14, wherein the first fusing portion is formed by providing anopening in the first connecting piece, and the first fusing portionincludes fusing sub-portions provided at two sides of the openingrespectively along a width direction; or the first fusing portion isformed by providing notches in the first connecting piece, the notchesare provided at two sides of the first fusing portion respectively alongthe width direction.
 19. The assembly for secondary battery according toclaim 14, wherein the first electrode tab connecting portion includestwo first electrode tab connecting sub-portions and a first electrodetab jointing sub-portion; the two first electrode tab connectingsub-portions extend along a length direction; the first electrode tabjointing sub-portion extends along a width direction, and two ends ofthe first electrode tab jointing sub-portion are connected with the twofirst electrode tab connecting sub-portions respectively; the firstelectrode terminal connecting portion is positioned between the twofirst electrode tab connecting sub-portions and extends along the lengthdirection; the first fusing portion extends along the length directionand is connected between the first electrode tab jointing sub-portionand the first electrode terminal connecting portion.
 20. The assemblyfor secondary battery according to claim 19, wherein the assembly forsecondary battery further comprises an insulating piece adhered on asurface of the first connecting piece which faces the electrodeassembly, and the insulating piece covers two edges of the firstelectrode terminal connecting portion along the width direction.